[CQ] Numeric issues: fix implicit casts

[pq]

Implicit casts can lead to lossy conversions.

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read the Flutter Style Guide recently, and have followed its advice.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel on Discord.

[jwren]

LGTM, I am all about general cleanup PRs, we also want to make sure though that the better cleanup here isn't to just remove the files entirely :)

[pq]

Heh. I actually forgot to add a question to this PR. Thanks for noticing!

You're dead-on. FlutterFramesMonitor is potentially unused (or only indirectly) and I've added to a list of classes to consider for removal. Thanks!